Coronary artery bypass grafting (CABG) has traditionally been performed with the use of a cardiopulmonary bypass (CPB) machine to oxygenate and perfuse the body during surgery. Recently, techniques have been developed to allow for performing CABG without the use of CPB by stabilizing the epicardial surface of a beating heart at the coronary anastomotic site with a stabilizer (e.g., stabilizing feet) to allow placement of sutures through the graft vessel and recipient coronary artery. This procedure may be performed through a partial or full sternotomy, or via a thoracotomy (which is an incision between two adjacent ribs).
A challenge to beating heart surgery is that some hearts do not tolerate the necessary manipulation (e.g., movement of the beating heart into position for surgery and stabilization of the site on which surgery is performed) well from a hemodynamic standpoint. Currently, when the beating heart is lifted or twisted (to access the portion thereof on which surgery will be performed), the cardiac output drops, often to dangerously low levels.
There is a need for a pumping apparatus capable of assisting the beating heart during surgery, to compensate for decreased hemodynamic function (including decreased ventricular function) that results from manipulation. The inventive pumping apparatus is designed to perform this function.
Some pumping systems have been used to assist the beating heart during surgery. However, such conventional systems are subject to significant limitations and disadvantages.
For example, pumps (such as the Medtronic "Bio-Pump" centrifugal pump available from Medtronic, Inc.) have been used to pump blood from the vena cava during beating heart surgery. It has been proposed to use a system including such a pump (and an intake cannula and outflow cannula connected to the pump) as follows: the intake cannula is inserted into the vena cava, the outflow cannula is inserted into the pulmonary artery, and blood is then pumped through the cannulae from the vena cava and back into the pulmonary artery during surgery. However, this technique requires two incisions in the patient: one to allow insertion of the intake cannula in the vena cava; the other in the pulmonary artery to allow insertion of the outflow cannula therein. Undesirably, the latter incision must be made in a high pressure zone (the pulmonary artery).
As another example, the Hemopump Cardiac Assist System (sponsored by Medtronic, Inc.) includes a cannula for insertion through an incision in the ascending aorta into the left ventricle of a beating heart. The cannula includes (and encloses) a pump. The pump is a rotating Archimedes screw whose intake is the distal end of the cannula (which is positioned in the left ventricle) and whose outlet is positioned in the ascending aorta. In use, the pump continuously pumps blood from the left ventricle into the aorta. However, this apparatus assists the left heart, rather than the right heart (which is weaker than the left heart). The apparatus does not inflate the right atrium or right ventricle, and thus does not provide the hemodynamic benefits which result from inflation of the right atrium or right ventricle during beating heart surgery.